Pagoda SL Group
W113 Pagoda SL Group => General Discussion => Topic started by: Bob G ✝︎ on August 01, 2003, 12:30:10
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My order from john Olson arrived today. Has anyone else received their springs? I would like to start a discussion group so we can all communicate on our progress with these new profgressive rate springs.
Bob Geco
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Mine arrived on the doorstep yesterday, each snuggled in its own foam blanket, all shiny and bouncy, tipping in at a healthy 10 pounds apiece. My new quints.
It will be 5-7 weeks before their new host is out of body rehab, but I'll report as soon as they're safely tucked in.
'71 Tobacco/Cognac 280 SL #22375
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Hi Guys,
Springs arrived on Friday. One rear spring is off the car already. Just ordered new top and bottom spring pads and bushings for the trailing arm. The top spring pad was in good shape. About 80% of the bottom spring pad was missing. Trailing arm bushings were cracked pretty severly. I've got to buy a 35mm socket to remove the trailing arm from the rear axle. I don't know about you guys but when I'm doing a project in a certain area of the car I tend to expand out from the original let's say "spring project" into related stuff like bushings. Projects take longer but I try and do them the right way so that I don't ever have to go back over that area again.
I put the new and old springs next to each other and they appear to be twins. Same height and it looks like same size coil. What makes our new springs progressive? It must be something like tempering of the steel because nothing is obvious from an outside comparison.
Good luck,
Jeff
1970 280Sl 4 speed w/three springs
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I always thought progressive coil springs had a tighter wind ath the ends and a looser wind in the middle. Maybe you had preogressive springs alreaady. If you have the time and the means, can you post a picture of the two side by side?
Rudy
Los Angeles
1971 280 SL
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I'll post pics of the new and old springs later today.
Jeff
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Jeff, the bolts that hold the torque arms to the axle can be difficult to loosen. I tried without success, simply could not get enough torque on them (I bent back the lock tabs, too). Took it to a shop, the tech used a lift, a long cheater and his full body weight to loosen them. I hope it goes better for you!
George Davis
'69 280 SL Euro manual
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Thanks for the advice George. I suspect it will be difficult to loosen the bolts. I use the handle from my hydraulic floor jack when I have sticky bolts. Fits nicely over the handle of my 1/2 socket wrench.
Jeff Clute
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Thanks for the pic Lax, but I can't get the link to work. Sorry. If anyone else got it to work , please let us know and I'll try it again. Thanks.
Rudy
Los Angeles
1971 280 SL
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Thanks for the pic Lax, but I can't get the link to work. Sorry. If anyone else got it to work , please let us know and I'll try it again. Thanks.
Rudy
Los Angeles
1971 280 SL
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Rudy, Can't seem to send a picture correctly. Maybe because my site name happens to be an email address, I'm not sure. Send me your email address to lax882@aol.com and I'll send you a picture of the springs.
Jeff
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Here are Jeff's pictures of the springs. They don't "look" progressive.
Download Attachment: (http://images/icon_paperclip.gif) springs1.jpg (http://www.sl113.org/forums/uploaded/rudy/200385101316_springs1.jpg)
50.29 KB
Rudy
Los Angeles
1971 280 SL
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Lets hear from one of you who installed the springs and give us a report.
Bob Geco
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I found this interesting link. Seems accurate enough.
http://www.jontreby.fsnet.co.uk/CV/usa/Page001.htm
Rudy
Los Angeles
1971 280 SL
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I found this interesting link. Seems accurate enough.
http://www.jontreby.fsnet.co.uk/CV/usa/Page001.htm
Rudy
Los Angeles
1971 280 SL
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Rudi,
Thanks for posting my picture and for the article about progressive springs. On the surface there doesn't seem to be any special construction to the new springs. They look the same as the old ones. I'll have to look into this a little more.
George,
Took one of the trailing arms off this evening. It was on very tight. For those of you planning to change out the bushings you need a 35mm socket. Believe it or not a 1 3/8 inch socket is too tight. For the outside bolt it needs to be a very shallow socket. The lower shock absorber bracket would not permit me to use the socket driver. I ended up putting a pipe wrench on the socket to remove this bolt. This does present a problem in re-assembly because I can't use a torque wrench. I'm going to have to work around this somehow.
Good luck,
Jeff
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Thought I would let the group know about the trailing arm bushing replacement. Old bushings were cracked and dry on the outside edges. The inside part was in great condition and doing its job. Don't know if the job was worth the effort. I did notice that there is a nylon spacer which acts as the pivot point for the trailing arm. This was caked with gunk. My training arms were very stiff, meaning I could not easily pivot them up and down. You need to reove the trailing arm to clean and grease this spacer. While your at it clean up the clamp plate and lock washer. Both were a little rusty which contributed to the stifness in this fitting. The flexible mounting in the link arm attachment to the floor pan was very worm. It looks like it had worn in the rear side and was a little elongated due to the force of keeping the rear axle in place. I would definitely plan to replace this bushing.
Jeff
1970 280SL 4 speed
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Jeff and Rudi and fellow W113 Suspension Tuners,
First, I have double checked with the factory and they reaffirmed that all but one (you know who you are) of the W113 spring sets sets have progressive rate specifications. Additionally today I inspected an extra set(from this same group order) that arrived at my office: all five springs are progressive in design. This is not to say that an isolated packaging error might have occurred and anything like that will be replaced ASAP.
Rudi's link to the explanation about various kinds of springs (and various kinds of progressive rate springs too) is outstanding! Rudi, your expectation that the loops on one end will be closer together than on the other end is true, and should be true of all the springs delivered. The photo that Rudi(?) posted at of Jeff's new and old spring side by side is a bad angle to see the difference. On all five springs at my office the space between the loops grow from a half inch up to one and a third inch before reducing somewhat at the opposite end. The progressive rate we chose, starting at 12% stiffer than standard and climbing to 25%, is not a huge change, so the difference in the loops is a little subtle, but it's there. On the equalizing (AKA compensating) spring the change is even more subtle, but if you use a tape measure you'll see the gap between loops is over double the width toward one of the ends.
Jeff, if you lay your springs flat on their side, photographing straight at the side, the change should be disernable. If anyone's springs fail this test contact me directly and we'll deal with it.
Mit Vollgas (pedal to the metal)! :) John Olson (Inc).
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John, I just want to make it clear that my only interest in these springs is from a technical curiosity, and in no way did I intend to imply you weren't delivering what you promised.
Rudy
Los Angeles
1971 280 SL
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John, I just want to make it clear that my only interest in these springs is from a technical curiosity, and in no way did I intend to imply you weren't delivering what you promised.
Rudy
Los Angeles
1971 280 SL
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Hello John,
Thanks for your email. I'll send you some better pictures in a few moments. All of the springs appear to be the progressive type. One end is more tightly wound than the other.
First some measurements. I lined up the pairs of springs next to each other and recorded the following :
Rear springs
left right
top loop 7/8" 13/16"
bottom loop 1 3/16" 1 1/2"
Front springs
left right
top loop 1/2" 5/8"
bottom loop 1 1/8" 1"
If these variances are within tolerance great. I have no way of knowing. As you can see the largest variance is in the bottom loop of the rear springs. 5/16" is easily noted. You indicate the equalizing spring change is more subtle than the front and rear. In my set this spring is clearly the most visibly progressive. One half of the spring is very tightly wound and differs significantly from the other half. I'll send off the pics in a few minutes. Please let me know if the springs are within tolerance.
Thank you
Jeff Clute
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quote:
Originally posted by Lax882@aol.com
If these variances are within tolerance great ..<<snip>>.. Please let me know if the springs are within tolerance.
Thank you
Jeff Clute
Jeff,
Your new report confirms you do have five progressive-rate springs. Measurements vary spring-to-spring because the specifications are custom made spring-by-spring to comply with the deflection rates at different stages of compression. Each of your springs was tested during and after the heat treatment (hardening process) for compliance before shipment. Slight variations may also be seen in uninstalled height; that will be further reduced or gone when installed with the full weight of the car. The existence of six different front spring pads thickness' reflects inherent differences, left to right and front to back, that M-B themselves faced. Variations in the cars are also responsible for some of those unequal measurements we found in all the cars in the beginning. It goes without saying these differences can not be totally eliminated in a group order. What everyone should notice/enjoy immediately is perhaps the most important: reduced body lean and less nose-dive in braking. A less "busy" body.
John Olson (Inc.)
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John, Thanks for your comments. I am close to installing the rear springs. I noticed that the top of the old rear spring straigtens out at the very end of the coil. If I use this same orientation with the new spring the progressive end (tighter winding) will be down.
The Haynes Manual and other documentation indicates that the straight end of the front spring indicates the bottom. If I apply this same instruction to the new spring, the progressive end (tighter winding)of the spring will be on top.
Please advise if this is correct? Likewise how is the compensating spring to be oriented?
Thank you,
Jeff Clute
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Jeff's question, if I read it correctly asks if it matters which end of a progressive rate spring is at the top. It does not matter as springs retain their designed behavior regardless of orientation.
Side Note: I just revisited the link on coil springs that Rudy provided (http://www.jontreby.fsnet.co.uk/CV/usa/Page001.htm) and noticed that the action drawing of a progressive spring going up and down has a technical error -- it shows the wider coils contracting first followed by the tighter loops. For those of you that like this kind of minutia, it is actually the tighter wound loops that contract first as that portion of the steel is longer than the end of the coil with wider spaced loops. Said another way, if you marked the coil half way between each end (7 inches across a 14 inch coil) and then ran a tape measure from the mark out to each end of the coil, the "half" with tighter loops will be longer. The longer a piece of wire the easier it bends.
Please direct future questions to my e-mail address. It will not be possible for me to be a regular W113 Forum participant (even though I've enjoyed three visits here in one day!). I'm often available by phone for quick questions too(612-377-0155), especially for customers and SL Market Letter subscribers! :) John Olson (Inc.)
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Can someone help me out. I am more of a visual person when it comes to mechnical repair. Can someone take some detail photos of what needs to be undone to switch out the rear coil springs & pads & the compensator spring & Pad. Please also list what other parts beside the spring pads need to be purchased and should be replaced. This is given nuts & Washers.
Is the front a bigger job and what is involved. Can some one make a refference to the BBB manual pages /job I don't know if something like this is listed.
Thank you for the help.
Bob Geco
1968 280SL
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Bob - I have not switched my rear springs but I have taken them out. IMHO, you don't need to replace any washers etc. Changing the pads should not be necessary, unless your old ones are briddle, broken etc.
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JohnOlsen - why don't you just have the factory send the spring's force vs vertical displacement curve for each spring delivered.... if, as you say the individual spring's heights and coil spacings are 'tuned' to a given force/displacement specification then there should be a measurement verifying same that can be sent with each spring.... in which case the material constants for a given spring (modulus of elasticity, wire diameter) are taken into consideration in the net result (force vs displacement).
By the way, the displacement as function of force varies in direct proportion to the force, independant of the winding's distance from one another in each segment of the coil (say 360 degree segments for simplicities sake)... all other things equal.
For a cantelever beam --- which is what the coil spring approximates:
y = FL^3 / 3EI
where y = vertical displacement
F = applied force
L^3 = cube of the coil's wire length per segment
E = modulus of elasticity (psi)
I = Moment of Intertia --- function of wire diameter.
So, for a constant material (modulus), and wire diam (I), the displacement of the spring as function of force is
y = FL^3(k) where k is the constant for a given spring (1/3EI)
If you divide the spring into each of it's windings for convenience, then each winding has Length L(sub i)... those windings the furthest apart having longer L / winding... therefore larger displacements than the windings the closest together (at windings measured at rest with zero force applied).
The sum of the y (sub i) for each winding as function of force applied to the end of the spring gives the total displacement of the spring as a function of force.
You'll notice that L (sub i) cubed is constant for each 360 turn of the winding.... so the displacment for each section of the winding is linearly proportional to the force applied for each section of the winding.
I bring this up because it also means that the sum of the displacements over all windings is also a constant for a given progressive spring... meaning that the displacement of the whole spring is also linearly proportional to the force applied for the whole spring.... therefore the 'progressive' nature of the spring escapes me.
Seems to me from the above mechanics that these 'progressive' springs are simply stiffer springs than normal... i.e. either larger diam wire or higher modulus spring material than the standard springs. Unless or until one or more of the adjacent windings reach one another to stop any further motion of that winding, there is no change in the linear response of the spring compared to any other... it's just stiffer. The only other way they could be considered 'progressive' is if any of the winding segments exceed their elastic limits... in which case the springs simply get shorter ... permanently, but the spring rate doesn't change.
Can you provide the mechanical basis (mechanical engineering reference) for describing these 'progressive' springs as anything more than just stiffer springs?. Just so I'm communicating clearly, if you were to draw a graph of the spring's displacement vs force applied, with the displacement on the vertical axis and the force on the horizontal axis, the stiffer spring would have a less inclined line (lower slope) than the normal stiffness spring, but both would be linear over their elastic range. Neither relationship of force to displacement would show a curve bending flatter (as is implied by the description of the 'progressive' spring) unless and until the spring's elastic properties are exceeded... normally referred to as ruining the spring.... or unless and until part of the spring's coils bottom out on one another... not something springs are normally designed to do since this also causes metal to metal contact leading to premature wear, not to mention noise.
I'm just curious what the force displacement curves are for these 'progressive' springs... being a mechanical engineer it isn't apparent how these springs are 'progressive'.
Longtooth
67 250SL US #113-043-10-002163
95 SL500
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JohnOlsen - my prior note on this topic was a longwinded technical explanation of my understanding of these 'progressive' coil springs. What I should have said is that I don't see what makes them 'progressive' from a mechanical analysis of elastic beams... but more to the point,
What are the specifications for the force vs displacement relationship of these 'progressive' springs compared to the 'standard' or some other set of 'stiffer' springs? Are the spec's numeric (i.e. quantitative) or generalized non-quantitative?. Where are the spec's on spring rate vs force available?
Longtooth
67 250SL US #113-043-10-002163
95 SL500
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Wow...this is getting technical. I just want my car to hang it's a** end out on on ramps at 90 miles an hour, and not bottom out.
Rudy
Los Angeles
1971 280 SL
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Longtooth,
John Olson (check your spelling) indicated to send comments & questions directly to his e-mail account as he could not promise to visit our forum on a regular basis.
Thanks,
Rodd
1966 230SL Euro
1994 E420
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I have taken the liberty of forwarding Longtooths comments to John Olson. Hopefully we will all get an answer soon. Should be an interesting item to follow.
Jeff
1970 280SL 4 speed
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Well ... all I know is that when I drove Tom Sargeant's car with the springs he purchased from John Olson, the car drove as smooth as mine (i.e. the springs did not feel any stiffer) except that when it came time to take a fast corner, or brake hard, the lean and dive were vastly different from what I know my car will do under the same circumstances. So: same ride under normal conditions, no stiffer or harsher than normal, but greatly improved handling under more strenuous circumstances. This is what these springs accomplish and I understand Longtooth's interest in knowing exactly how they work, as a technical engineer (I can at least follow some of his post, but not enough :-( ) but I don't think we'll benefit much from continuing this very technical discussion here.
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Cees - Stiffer springs won't necessarily give you a different feel at low forces relative to the standard springs.... the difference in displacement being very small ... probably below a threshohold of subjective "feel". But, as the force increases the difference in displacement increases proportionately so that at very high forces the difference in discplacements are pronounced.
As an example, just for illustration purposes (I don't know the actual spring rate stiffness's) let's say Standard Spring's stiffness is 10 kg/mm (0.1 mm/Kg), a stiffer spring (double the stiffness of the standard spring) is 20 Kg/mm (0.05mm/Kg).... that's 20 Kg force for each mm of displacement or conversly, 50 microns/Kg of force.
Let's assume further that the springs with no load are 300 mm long (~ 12 ").
Now, assume the weight of the car with occupant(s) is 250 Kg load per spring... so these springs compress in length by 25 & 12.5 mm respectively (standard vs stiffer spring) before any other forces are applied while driving.
Under normal driving the added forces due to ruts and bumps are a fraction of the at rest load per spring.... so for examples sake, assume up to another 50 Kg's force per spring are applied .... the additional displacement for each of these springs is 5mm and 1mm respectively (for English measures, that's ~ less than 1/4" & less than a 1/25th") respectively for the standard and stiff spring.
It's not likely you'll 'feel' any difference under low forces.
But, at very high forces... say hard stops or high speed cornering... the spring's applied loads increase over dead loads due to acceleration (mass x acceleration (or deceleration) = force), so at the extreme, I'll assume an acceleration of 3x... which is to say an acceleration of 3x more than that due to gravity alone. This means that each spring will receive a maximum applied force at the peak of this acceleration (deceleration) of 3xthe dead weight on each spring... in this example, 3 x 250Kg/spring = 750 Kg's added load (over dead load). The displacement of the standard spring under this condition is 75mm (~3"), while that of the stiffer spring is only 15 mm(a shade over 1/2").
Note that while the ratio of displacements of these springs are ~5:1, the low load conditions don't cause an appreciable difference in 'feel', while under high loads there will be an appreciable difference in 'feel'.
This was just an example... not to be construed as a comparision of John Olson's 'progressive' spring and the standard spring, since I don't know the spring rates of either in fact.
I do know the curb weight of the 250SL... 1360kg, and the ground clearance with full permissible load (1715Kg) which is 125mm (from Service Manual spec's).
The front/rear axel weights are 830/885 (Kg).... so ratio of 48%/52%. ... or for front standard springs a max 'permissible' dead load of 415 Kg/front spring.... so my example spring's assumed a load of 60% of that or 77% of the curb weight/front spring. It doesn't change the displacement numbers I used, but the base assumptions for spring's length and loads are in the general ballpark.
Also you need to bear in mind that the shock absorbers will take up a greater proportion of low force displacements due to accelerations/decelerations, bumps, etc, while a small proportion of the high load conditions... another reason why you are't likely to be able to 'feel' any difference between a standard spring stiffness and high spring stiffness in normal driving conditions.
As for our notorius front end dip at stops, while the front spring's are compressing under the deceleration at stops, the rear spring's are going into tension.... i.e. equal and opposite force on the springs (front end dips and back end rises... comensurate with the difference in spring stiffness's of front and rear springs), so the actual displacements you feel are due to the combination of all spring's on the car... not just a single spring's condition... i.e. another way of saying this is that a stopping force causing compression on the front springs is divided between front and rear set's of springs...i.e. the front set is trying to hold the car up on that side, the rear set is trying simultaneously to pull the car back down on that side... but with a lesser force since it's only got the dead weight of the rear to deal with... no acceleration condition on the rear springs exists when 'stopping' (the converse is true when accelerating away though).... that's just another reason why you won't likely feel any difference in spring stiffness's under normal driving conditions, but will feel the difference in extreme conditions between standard and higher stiffness springs.... which has nothing to do with the higher stiffness set being 'progressive' as has been described by John Olson.
The 'progressive' spring (and such spring's exist) requires either a progressive change in modulus along the winding's length from one end to the other, or a tapered diameter... i.e. progressively thicker (or thinner) diameter of wire within the coil. The former (changing modulus) isn't an economically practical means of obtaining a progressive feature for consumer springs... maybe for Nascar or Indy racing but not otherwise,... so a consumer 'progressive' spring will have to have a difference in the diameter of the coil wire from one end to the other to be truely 'progressive' (i.e. progressively increasing spring rate (or progressively increasing the force/displacement spring constant as loads increase) not just 'stiffer' as in the common use of the term by the layman.
It would be interesting for one of the new purchasers to measure the diameter of coil winding wire along the length of the winding from one end to the other. Compare those (or that) diameter to the diameter of the wire in the standard spring, since it's very likely that the tensile 'elastic' modulus (Hooke's law for those that know what I'm talking about) of the springs are very nearly identical... spring's being made of similar steel composition with similar heat treatment & quenching to achieve the requisite compromise between 'brittleness' yet high modulus with elasticity required of springs used in automobiles.
More interesting yet though (& direct) would be the comparision of the standard and 'progressive' spring's force/displacment curves over the applicable load range.
Longtooth
67 250SL US #113-043-10-002163
95 SL500
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OK, I'll show my ignorance here. Why would a heavily braking car, nosediving all the way, not be considered to have an "acceleration" applied to the rear end of the car as it lifts? Also, all math aside, a stiffer spring can absolutely be felt at even the slowest speeds given a similiar "bump" to roll over. I have a 95 Chevy Suburban 2500, with a 454 supercharged engine and Brembo brakes. When we out in "stiffer" springs, the ride of the truck, at even the lowest speeds, became noticeably worse. Conversely, the high speed ride became much better, with much less body movement even in a straight line. I admit in advance I may be missing the point of the previous lesson.
Rudy
Los Angeles
1971 280 SL
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Rudy, the acceleration does exist on the rear springs during nosediving stop.... but the maximum force that can be applied to those springs in that case is only the weight of the undercarriage at the rear axles (tires, wheels, swing arm axles... perhaps the rear-end if it's not attached to the car body ... as in my '65 Chevy HD 3/4 Ton Long Bed)... in effect all you're doing is lifting the wieght of the car body off the rear springs.... therefore you don't multiply the acceleration factor times the mass since the max mass is only the suspended weight of the axles on the rear springs.
As for your suburban with stiff springs, it sounds more like my '65 Chevy Pick-Up without a load in it.... the springs are stiffer than the shocks so you're feeling the springs before the shocks begin to have an effect is my best guess. When my pickup has a 1/2 ton or 1 ton load in the bed the truck rides much, much smoother, ... because the rear springs have been compressed already to the point where the shocks are taking on the high frequency accelerations instead of these being transmitted directly thru the springs (which don't respond to high frequency accelerations since high mass (loads) can't respond quickly to the high frequency changes.... (small acceleration's of very short duration).
The point of my prior note was simply that under normal driving conditions in an SL the shocks will absorb the short, higher frequency accelerations, the springs the low frequency high accelerations.... and you'll notice no difference in standard springs and 'higher' stiffness springs until the accelerations are high enough (low frequency) to be mostly absorbed by the springs. The notorious nose dive will be reduced with higher stiffness front springs.... (a low frequency high acceleration condition which aren't absorbed by the shocks before the springs).
I'm requesting some objective specifications on the spring rate change of the so called 'progressive' springs relative to standard springs on the SL. From what I can tell... from what's been stated and published on these particular 'progressive' springs there's nothing I can see or which is stated that makes them 'progressive'... rather simply stiffer.
Longtooth
67 250SL US #113-043-10-002163
95 SL500
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Well Longtooth, I can't beleive it, but I actually get it now. And I agree with you. Riddle me this though. Is it possible that a progressive spring can actually cause an "ndesireable" change in handling charactersitics, like a change from neutral to slight oversteer, to MASSIVE oversteer at a car's maximum grip handling limit. I admit we're talking about a rarely seen very high limit, but cars have been known to exceed their limits. I'm not talking about a car's handling tendancy, I'm talking about unexpected attitude change.
Rudy
Los Angeles
1971 280 SL
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Well Longtooth, I can't beleive it, but I actually get it now. And I agree with you. Riddle me this though. Is it possible that a progressive spring can actually cause an "ndesireable" change in handling charactersitics, like a change from neutral to slight oversteer, to MASSIVE oversteer at a car's maximum grip handling limit. I admit we're talking about a rarely seen very high limit, but cars have been known to exceed their limits. I'm not talking about a car's handling tendancy, I'm talking about unexpected attitude change.
Rudy
Los Angeles
1971 280 SL
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Longtooth,
I have measured the diameter of the old and new rear coil springs. Both springs use 16mm diameter wire. There is no variation in end to end wire diameter on either spring.
Jeff
1970 280SL 4 speed
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OK, I hate to do this because I am no mechanical engineer, but I have to get into this conversation for a couple reasons.
1. John requested in his post that questions be directed to his e-mail account, not to this forum. So I would assume your request will not be satisfied here since John does not plan to visit our forum very much. He did so as a courtesy to his customers on this forum.
2. If you write John directly, I would do so with a pleasent tone, not one that could be interpreted as confrontational. Please don't allow him to think you are accusing him of ripping off his customers. When we write, there is no way for us to impart voice inflection, body language, facial expressions, or any other form of interpersonal communication. Please take care in what you write. John's web site (www.slmarket.com) also lists his phone number.
3. Has anyone posted a side-by-side pic, taken from a 90 degree angle, of the different springs? The one pic was taken from about a 45 degree angle. This would help our understanding.
4. Now, to my novice understanding of these springs and our discussions of them. This is fun!
- Yes, it would be nice to receive mechanical data from the manufacturer, but I would think only a small percentage of their customers want to know (or could understand) this technical information. It is probably not worth their time to supply it.
- In Longtooth's first big post, he says that,
"You'll notice that L (sub i) cubed is constant for each 360 turn of the winding.... so the displacment for each section of the winding is linearly proportional to the force applied for each section of the winding.
If I understand this, he is assuming that each 360 degree coil is the same. I think that's the whole point of a progressive spring is that they are not the same. If there is 3/4" between coils at one end and 1-1/2" between coils at the other end, then there must be more material to make that longer coil. It's longer because it climbs more vertical distance in the same radius. If it's longer, then it will bend easier. Right?
- An assumption is that the steel is a constant thickness. It was measured 16mm at each end, but is it consistently 16mm from end to end?
- An assumption is that the steel is a constant hardness. Could part of the spring provide more bending resistance than another part of the spring simply by the way the metal was manufactured? I don't know if you can harden one part of a piece of metal more than another part.
Just some random thoughts!
Rodd
1966 230SL Euro
1994 E420
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Rodd, Thanks for your thoughts. I will be happy to send some pics. I have tried before to do this and failed. The problem may be my email address is my login name. I would like to change that if possible.
If you like I can send the pictures offline to you and you can add them to the site.
Anyway the new springs do not vary in thickness from top to bottom (end to end). You know a better term to use for these springs may be "variable pitch". You are correct the winding is much tighter on one end then the other. The stock springs are uniform throughout, with the exception of the very ends on both sets. The variable pitch springs are just that. The angle of the winding differs from top to bottom. On one end, I'll call bottom, the angle and spacing of the winding exceeds the factory springs. At the other end, I'll call top, the angle is flatter and the spacing tighter than the factory springs.
One other note. The overall spring length is the same as far as I can tell. Same height. Same diameter wire. But different pitch for sure.
Should receive my bottom spring pads tomorrow so I can install the first rear spring. Decided to do one side at a time to keep the rear axle steady.
Jeff
1970 280SL 4 speed
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Rod, your points are well taken with regards to asking John Olsen directly instead of indirectly on this forum... as well as being non-confrontational. There's a reason why I haven't sent an e-mail directly to John Olson.... that reason being simply that I intend to remain an anonymous member of this forum. The only source of my actual identity can only occur by the owners of this website... which is fine and any further association of my pseudonym with my identity is governed by the privacy policy. Certainly somebody could look in public records for my SL's VIN and probably identify me that way too... but I prefer my anonymity to be generally anonymous and remain so. I've been using PC's and web since inceptions... I've discovered there are those who may use other methods to harass posters when they are unpopular or go against somebody's sense of what's o.k. or not o.k. as the case may be... provided they can find the real identity.
That addresses why I have only indirectly questioned John Olson's statements on this forum rather that e-mailing him.
From the outset of my posts on this topic I've questioned the nature of the 'progressive' spring description as described on John Olson's web-site and the interpretation of the use of the word 'progressive' as applied to the springs offered on that web-site. I've done so because as a mech. engineer I was curious about how a coil spring could progressively increase it's stiffness as function of applied loads to the spring.... and my 1st order quick analysis of the physics and mechanics of springs didn't lead me to see how this could be achieved with a single coil spring.
At the same time, my understanding from a mech. engineer's point of view not withstanding, I hedged by requesting (from anybody, but specifically in my note responding to John Olsen's response) the objective quantitative description of the change in stiffness as function of loads. My thoughts were (and still are) that perhaps there's some aspect of springs that aren't governed adequetly by the general equations describing displacements of beams under load... though I haven't come across any subtlties yet in practice, I don't normally work with coil springs, rather almost exclusively with beam springs (though coil springs are just a specific type of beam), so it was certainly possible my treatment of said spring's were not taking something for which I was unaware into consideration.
Over the course of further analysis I now find and continue to confirm my initial quick analysis... and the additional analysis includes varying the modulus or diameter or both along the length of the coil winding. It makes no difference.... these changes, nor changes in winding pitch can change the stiffness of the spring as the load increases. In short, I have found no way to make a single coil spring behave progressively stiffer as load increases.
(for the layman, Stiffness is the ratio of loading Force per mm displacment... or the inverse of Stiffness is mm displacment/unit load force. Increasing stiffness as load increases means the ratio of load to displacment increases as load increases.... the description of a 'progressive' spring has been described as increasing stiffness as load increases).
I am indeed questioning the progessive nature/description of the springs described ... and IF such questioning is taken to be 'confrontational', then I believe this will only be in the eyes of those who feel 'confronted'. To avoid this if possible, however, I have asked for the quantitative spec's of said progressive springs (indirectly on this forum). I believe this is warranted by virtue of the facts.... predominantly for 2 simple reasons ---
1) There's been no quantititive description of the variation in spring rate as function of force... nor do the physical dimensional descriptions on this forum describe (this far) a progressive spring. The only difference thus far described is a variable pitch, which doesn't distinguish a progressive from a standard (non-progressive) spring (I've described this once in terms of L(sub i), but will give another description to explain this again later in this response). The other description (today) further says there's no difference in wire diameters from one end to the other... though it's perhaps yet to be determined whether there's a difference from ends toward center. As regards this latter possibility though, it still won't change outcome.... I also describe this later in this response.
2) The descriptions on John Olsen's web-site don't describe features of a progressive spring.... they only refer to 'firmer' ride under hard cornering/breaking.... a condition which also describes a stiffer spring with no 'progressive' feature.
"Simply stated, our Progressive Rate Springs become firmer the more they are compressed."
and
"... Springs give a comfortable ride during easy driving and become 25% to 30% firmer during hard braking, cornering, and emergency maneuvers."
"firmer" than What? Firmer than a standard spring only means stiffer... not progressively stiffer as forces increase. "firmer" can also be interpreted to describe simple perceived increase in resistance under hard braking and cornering as forces increase... which is all that occurs with any spring... the degree of resistance dictated by it's stiffness only... not a progressive feature.
The web-site offers no quantitative description of the progressive spring relative to standard springs or in absolute terms. At $800 a crack for set of 4, and for Mercedes drivers especially, as desciminating as we're likely to be, it would only seem logical in marketing to a descriminating audiance to include a quantitative description that distinguishes a 'progressive' spring from a standard one.
I'm frankly quite surprised nobody who's purchased or contemplated purchase and posted same on this forum has not asked for and subsequently then posted a quantitative description of the spring-rate as function of forces applied. More importantly, neither did John Olson when he responded at least 2x on this forum to some questions posted by purchasers. Interesting (to me).
That said, I'll address the L(sub i)cubed question you had.
Length Segments - L (sub i) Re-Addressed:
No, L(sub i) cubed doesn't care whether the winding pitch changes thru the course of the spring. The (sub i) simply describes the specific sub-length segments of each part of the spring from one end to the other...whether the sub-segments are at 360 degree intervals, or at equal 5mm intervals, or at any other sub-lengths.
The sum of the L(i) segments equal the total unwound length of the wire from one end of the spring to the other. So if the total Length of the wire is the same, then the stiffness is the same, and there's nothing in lengths or sublengths that will change the spring to a progressive type... regardless of pitch (proviso --- that under full allowable forces, one winding doesn't reach a 'stop' by being compressed metal to metal against another adjacent winding).
Changing the length of the spring doesn't change it to progressive... no matter any difference in winding pitch from top to bottom of the spring.... Total length of winding change, changes the spring's stiffness only...(total vertical displacement as a function of applied force)... in unit force/ unit vertical displacement.
Addressing Whether Changes in Wire Diameter or Modulus along the Length of the Spring's windings can make a Spring "Progressive":
Since I've become more and more interested in how the mechanics of a 'progressive' spring can be made to work, I've done some additional analysis. The result is that, surprisingly, neither a changing modulus (hardness if you want) over the length of the winding, nor a change in the diameter of the wire over the course of the spring's winding will make the spring 'progressive' as in increasing stiffness as function of force. In other words, I haven't been able to find a means of making a spring 'progressive' by any changes in pitch, Length, or changing it's Modulus over the length of the winding, or changing it's cross section (diameter) over the course it's winding.
The the bottom line is I cannot find an engineering method of making a spring behave 'progressively' as in change in spring rate (i.e. changing spring stiffenss as function of applied force, as opposed to simply increasing the spring's resistance to displacement as function of applied force... which is simply a constant stiffness spring). I can make a spring behave progressively, but not using the spring steel material in a single coil spring alone --- see below for a description of a progressive spring.
Increased Suspicions
Of course, this makes me more suspicious of the use of the word 'progressive' in terms of 'firmer' as used on the John Olsen web-site. What I now believe the use of the word 'progressive' in the descriptions on that web-site to mean is that it means 'progressively more resistant to displacments' as forces increase. This just describes the nature of all and any spring... all springs are progressively more resistant to displacement as force on the spring increases... it's the fundamental description of 'stiffness'. In other words, a 20% to 30% 'firmer' ride means a spring that's 20% to 30% stiffer than a standard spring. I seriously doubt the word 'progressive' means anything more than this. And, as I desribed in my 1st note on the topic by a quantitative example, a plain increase in stiffness doesn't necessarily mean it can be felt under normal driving conditions... but will almost certainly be felt in hard cornering and in braking by reduction in the W113's notorius nose-dive.
This isn't to say I'm sure about being right on this issue. It IS to say I am unable to find an engineering or physics foundation for a coil spring with a 'progressively' increasing stiffness as load increases.... and must therefore conclude the word 'progressive' as used on the John Olson web site is more appliable as a marketing terminology than an actual physical description of the spring's behavior... (until somebody can describe the mechanics that shows how a single coil spring (without other features on the spring) can become progressively stiffer).
Quantitative Analysis of Changing Wire Diameter over Course of Spring Windings:
For a quantitative example of the fact that a change in the cross section over the course of it's winding's length doesn't affect the 'progressive' change in stiffness of the spring, I'll use a changing diameter over the length of the winding (change in diameter of wire), assume a 5/8" wire of Length L = 1/2 total L of winding wire. Assume the other half of the winding length has diam 5/8" + 1/16". The difference in stiffness of one half to the other is 9%... the thicker section being 9% greater in stiffness than the thinner section. The 9% increase comes from the change in moment of Inertia (I) in the spring displacment formula, y = FL^3/3EI. For a circular cross section, I = (pi x r^4)/4 where r= radius (half the Diameter) of the wire windings. When you work this out for a 5/8" diam wire vs a 11/16" diam wire, the larger wire diam has a moment of Inertia which is 9% greater than the smaller one.
Since each half is acting in parallel (springs connected in series ACT in parallel in the Resistance model ... springs connected in parallel ACT in series) the combined stiffness of the total spring is 1/St =(S1xS2)/(S1+S2). Since S2 can be described in terms of S1 as S2=1.09 x S1 (9% greater stiffness of segment S2 relative to segment S1), if each are of the same length (0.5L in this example), then 1/Stotal = (1 x 1.09)/(1 + 1.09) = 1.09/2.09 = 0.52x = 1/Stotal. Then Stotal = 1/0.52 = 1.92 the stiffness of segment S1 acting alone.
There are a couple of important points here....
1) Varying the diameter of the spring's wire over it's winding length doesn't make the spring progressive... it just changes it's stiffness... it doesn't increase it's stiffness as a function of increasing applied forces.... which is what a 'progressive' spring has been described or thought to mean.
2) A very small change in diameter (in this example a 1/16th inch increase in diam over a 5/8" diameter base) in one part of the spring can have a major effect on stiffness of the whole spring.
A General Analysis of Force vs Displacment Equation for Springs and Cantelever Beams:
If you examine the equation which determines the spring's displacement as function of force (the above equation for y =...), you'll see that all terms except L are linearly related to each other, so that if L of the total spring is some fixed length, then no changes in the other terms for any sub-segement of L can change the overall stiffness as force increases, since the stiffness is the ratio of displacement to force applied... a linear relationship no matter what.
Changing the force F doesn't change the independant terms "I" (function of cross section), "L" (total length of winding), or "E" (modulus of material...either with differences in segments along the length or as a constant over the entire length). So it should have been obvious to me in the begining that the term 'progressive' couldn't mean a spring's stiffness can change over the course of increasing forces applied to it as long as the spring's material stay's within it's elastic limits. By the way, if the forces applied to the spring cause any portion of the spring to exceed it's elastic limits, then the spring length becomes shorter (i.e. from top to bottom... some sections of the spring pitch will decrease) ... permanently. The total winding length (L) doesn't change though, so the stiffness remains constant, however the drawback is that when pitch between one or more windings descreases because the spring was overloaded then the spring stiffness at the extreme overloading force increases by a factor related to the portion of the adjacent windings coming in contact with one another.
One Way to Make a Spring Behave Progressively:
If I were to make a progressive spring, it would have some rubber cushions BETWEEN the windings with the closest pitch... leaving a gap of some specific magnitude between the rubber cushions and one of the adjacent steel windings. Then at a specific force (load) on the springs, these rubber cushions would bottom out on the adjacent steel winding, and depending on the durometer of the rubber would act to increase the stiffness at that load and loads beyond... as the load increased further, the rubber is compressed more and rubber in other higher pitch windings would come into contact with their adjacent steel winding, etc.... increasingly increasing the stiffness of the spring as load increased... that would be one means of providing a 'progressive' spring.
Come to think about it, isn't that what Nascar and other racing vehicles do when they pit to change the 'wedge' ... add a wedge (of rubber between one or more spring windings) or take one out...? making the springs (on front or rear) or left or right side either more progressive or less progressive?
Another Type of Progressive Spring:
Another means of providing a progressively increasing stiffness as function of load would be to use multiple springs... one inside the other, nested, such that as loads increased, additional springs in the next would begin to come ito play and act to resist futher displacements... increasing stiffness as each new spring in the nest came in contact with the member attached rigidly to the frame.
Longtooth
67 250SL US #113-043-10-002163
95 SL500
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I would like to thank longtooth for explaining the coil springs to me. I understand now the way they work. I was under the false impression of progressive springs and how they, if they did exist worked and after reading the theory and thinking about how springs work I see that springs cannot be progressive alone. These cars were given a huge amount of thought by the builders and designers and they found the perfect combination of comfort and handling in the stock setup and any modifications or changes, I feel will compromise one or the other. The "progressive" springs as sold by John Olson may improve handling, however a harder spring im sure will ride harder. I prefer the stock setup almost always and over time have found most performance modifications in a vehicle compromise something- reliability, comfort or economy. I believe that the new springs may well be worth the investment, progressive or not, and may make your car handle better. a question I have is, how long to coil springs last. I have heard that they last a very long time and unlees they are broken they are usualy still as good as new. This info is not backed up by any facts and I would like to hear from someone who knows. Also if the springs wear, how do you check them, car height, overall spring lenght removed from car or using some testing equipment. Thank you
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Rudy, a few days ago you asked how changing springs (stiffness's) or if it can affect over-understeer or loosing it in extreme cornering conditions. The answer is I know it does, but am not exactly sure how this works in fact. You may note by reading the old automagazines when the 250SL came out vs the prior 230SL, one of the most dramatic and expected changes was to the suspension system... precisely because the 230SL had a high occurrance of suddenly losing the back-end unexpectedly (no warning by feel) on high speed cornering.
I also know that Mercedes designs in general are designed with a slight understeer at normal speeds (say at 15-20 mph over the 'posted' warning speed on higher speed not highly banked curves.
Unfortunately for me the whole topic of integrated suspension systems is one that I've always been curious about but have never taken the time to pursue in detail.
What I do know is that on high speed cornering, the lateral forces above the Center of Gravity (CG) provide a moment (Force x distance, where the force is Mass x Acceleration & distance is the vertical distance from CG to Ground) on the body that are trying to be countered by the tire's grip to the road. The moment above the CG causes the body to lean --- tilt is a better description --- so that the inner springs see lower loads while the outer ones see higher loads (btw, that's why stiffer springs keep the body of the car from tilting as much under higher corning accelerations... the outer springs don't compress as much, even though the moment above the CG remains the same).
As the body tilts more and more under cornering accelerations the outside axels have to begin to tilt also (since the center moves up as the body tilts, but the wheel hubs remain a relatively fixed distance from the ground on the outer axels.
This can be exaccerbated by lateral bending of the coil springs, moving the body slightly to the outside relative to the Axels... which moves the body's CG outwards while also upwards due to the tilt.
While this is going on the tires also begin losing grip with the road, begin to roll on the edge and tilt (along with the axel tilt) as the moment on the body increases.
The front tires are the ones directing the cars turn, so they're the ones seeing the most resistance to forward motion.... i.e. some of the direct forward motion (you know... body in motion tends to remain in motion in a straight line) is being redirected by the front tires in their turn... and of course due to the tilt (by moment) the outter front tire is receiving the highest resistance (force) on the tire's grip. This induces more tire roll on the front outer tire than on any of the others, and consequently less grip.
This phenomena should produce a component of understeer --- car tends to keep moving more forward than the steer would dictate. The driver therefore adds more steer to get the car to make the requisite turn on time... adding to both the force on the front tire, added moment on the CG, increased tilt. At some point the rear outer tire (which has less resistance the road because it's more/less just along for the ride while providing forward motion in a rear wheel drive) loses it's grip while the front outer tire is maintaining it's grip... which is when the car's rear spins out.
A stiffer set of springs reduces tilt so keeps the moment from increasing as fast... but this also just brings the point where the forces holding the tire to the road let loose suddenly with little 'feel' before it occurs... in other words, it's the body's tilt and a little sliding action that gives you some warning (with experience), so stiffer springs keep the body flatter (less tilt), and therefore the outer axels with less tilt for greater forces (lateral acceleration), keeping the outer rear tires in flatter contact therefore with more grip and hence higher lateral forces before they lose their grip.
By the way, it's interesting to note that the reports of SUV's which 'roll' over in emergency maneuvers have to have a CG that's so high that the car rolls before the tires loose their grip.... and probably higher mass so that the tire's actally roll over under lateral accelerations sooner too.... adding to the ability to roll the body over before the tires lose their grip.
One reason I like the W113's is their wide wheel-base and relatively low CG... the wider wheel base means that the moment has to be greater for a given degree of 'tilt' in lateral accelerations...meaning the moment is reduced even with it's relatively high mass... so it doesn't 'tilt' in cornering as much as would otherwise be the case, even with it's 'lower' stiffness springs.
Using higher stiffness spring's get's improved feel in cornering (less tilt), allowing the car to take corners at slightly higher speeds, but also brings the car closer to the edge of spinning out abruptly without the customary warnings before you reach the limit. To extend corning ability further yet, get the lowest profile, widest, stickiest tires you can find.... also the shortest springs and thinnest pads (lowers CG). You'll be able to take corners faster without spinning out, but when you hit the limit there's no recovery room.. and zero warning.... as our California wanna-be-Gov said in that movie..."hasta la vista, Baby".... which movie was that?
Longtooth
67 250SL US #113-043-10-002163
95 SL500
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That's interesting Longtooth. I know that new active suspension designs have the ability to make a car lean into a turn like a motorcycle. My understanding as to why they don't do that is because the people in the car basically freak out when this happens becuase it's counter-intuitive to what they expect normally.I personally have always liked cars that lean a bit in turns, but hang in there. My '64 Buick Riviera leaned but had incredible grip. I love the feel of my 280sl onn winding roads. Very fun to drive.
Rudy
Los Angeles
1971 280 SL
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Finished the installation of the two rear coil springs. Waiting on a spring compressor in order to replace the compensating spring. Just took an hour ride. First impressions: The backend of the car is firmer. Went through the gears several times and at 6K shifts the car doesn't sit down in the rear like it used to. Front comes up but rear end stays firm. I like it. Over regular bumps at regular speeds the rear feels great, nice but not too stiff. At hi speeds my rear end felt like it was skipping over bumps, it was pretty bouncy. I suspect the shock absorbers which have cracked bushings to be next on my list of suspension upgrades. I don't think to old shocks were able to keep up with the springs over these high speed 70-80 mph bumps.
So far I'm pleased with the change. I can't wait to get the other 3 springs on and drive it as a set. When you drive as fast as I did today you need your brakes and I really hate the nose dive.
I used the mid size top spring pad and my wheel well hieghts are 26.125 driver and 25.75 inches passenger. I recorded the same dimensions before and after the 20 mile breakin. The the lower part of drivers side rear wheel is slightly inside of the top part of the wheel. I may replace the drivers side top spring with the next smaller pad. The original ones on the car were both the thinnest version and they are in good shape so I'll reuse one if I decide to change it.
Jeff
1970 280SL 4 speed
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Sorry I'm unable to visit the W113 Pagoda SL Forum more often. As a purveyor of springs for Mercedes-Benz any discussion of suspensions is a welcome one! I became involved in supplying springs because M-B took me for granted by superseded an order I placed for M-B 280SL sport springs years ago; they sent standard springs without telling me. I didn't discover it until my suspension was dissembled. They just said "Sorry, M-B doesn't make the parts you ordered any more so our numbers reverted back to standard springs." Ugh. I had the springs I wanted custom-made and fifteen years later I have delivered many hundreds of custom springs, all for Mercedes-Benz, for all models from 1926 through 1980. Some have even been sold to Mercedes-Benz.
The availability of progressive rate springs is relatively recent.
I've accumulated much first hand experience during these years but do come to you "WSR" (without slide rule). I don't have the engineering background of some of you may prefer. I can draw on years of first-hand racing the infamous 300SL Gullwing and more recently a 300SL Roadster, including four La Carrera PanAmericanas (2,000 mile six day races through Mexico). My knowledge of suspensions comes from hand-on experimentation with dozens of setups including a personal 280SL five-speed (since sold but still loved). With this experience I've read your messages of this past week and believe following thoughts and facts should be added to the discussion in no particular order (you may want to download this and read it later; it's long!):
1) One writer observed that Mercedes-Benz engineers [I'd add their suppliers such as Sachs and Continental] put so much thought into each of their products that it is presumptuous for us to think we can second guess their decisions. Hmm, those same engineers would be the first to admit that every decision they made was a compromise. In cars sold to the public, suspension choices are many. Additionally, a two passenger car's wheelbase is short and its overall weight less compared to sedans. This alone magnify the effect of variable payload, not to mention where in the car the added weight occurs. Add diverse driver expectations (and abilities) and any standard SL is a watered down version of various potentials. In 1985 I had the honor of interviewing Hans Werner Aufrecht, one of the founders of AMG. He confidently stated that no matter what Mercedes-Benz offers for sale, he could improve on it. AMG has become an icon doing just that because Mercedes must take a far greater range of clientele into account than AMG. We, as discerning owners are pursuing the same thing as Herr. Eng. Aufrecht.
2) All three primary German shock absorber companies, Bilstein, Koni, and Sachs, employ the philosophy that it is the spring's job to handle the weight and downward (spring compression) strokes of a car and the shock absorber's job to mute rebound. Consequently the specifications even for adjustable German shock absorbers show 80% (plus or minus 10%) of their absorption on the rebounds stroke and 20% on the compression stroke. American shock absorbers are generally 50/50. plus or minus 10%. This may account for the difference reported among you re shock absorbers accentuating minor road variations at slow speeds, i.e. a Mercedes vs. an American car or Suburban.
3) Several e-mails pictured cars going out of control due to sudden changes in spring stiffness or suspension design. Of course all cars will go beyond driver control from overloading, poorly placed loads, too much speed, loss of road adhesion, tripping over obstacles, just to mention a few. Mercedes-Benz has been a leader curtailing these nemesis with "involuntary systems" such as anti-dive geometry in the 1980s, and ESP and ASD in the 1990s to shut down or correct for driver-naivety and their car's resulting trajectories.
Several of these hazards affect oversteer/understeer. Car companies declare "payload" maximums based of the strength limits of their parts but also to put a limit on oversteer from too much weight at the rear. This is not to say oversteer is always "bad." For decades race drivers preferred cars with oversteer. When front wheel drive cars became prevalent intentional understeer became necessary. High performance driving schools like Bob Bondurant's, prefer cars with close to neutral oversteer/understeer so drivers can shift the car's weight to whichever corner needs the most traction -- more over the steering wheels (via light braking) during the first half of corners and more weight over the driving wheels (rear for Mercedes) through acceleration after the apex of a corner (accomplished through so-called "heel and toe" footwork). In short, there is no one-fits-all answer, unless it is Bondurant's.
4) On August 15 Longtooth states as fact that the 230SL had significantly greater tendency that the 250SL for sudden oversteer.
FACT: I don't know which automotive journalist or author started this notion that there is a difference in the suspension amongst the W113 SLs but it is not true. Gernold Nisius set me straight on when he was proof reading my book THE SL EXPERIENCE before publication. There is no change whatsoever in the basic suspension components of the 230, 250 or 280 SL. I did previously know the springs retain the same standard deflection rates per 100 kilo. on all three models. Different springs are specified for preserving ground clearance of later cars delivered with A/C, automatic transmission, and power steering, but for no other reason. Major changes occurred on non-SLs during these years, but the only change to the W113 was a reduction in the number of grease fittings, and those changes were not specifically on wheel-to-body suspension parts (they were on the drive shaft and steering box). To come to the defense of the 230SL (are the rest of you 230SL owners sleeping?) it was that first model in which Rudolf Uhlenhaut is credited with lapping the Montreux race track within .2 seconds of a V12 Ferrari 250GT Berlinetta driven by Ferrari designer Michael Parkes (1963). It is also the 230SL which British automotive journalist L.J.K. Setright always favors as more agile than it's successors, the 250 and 280SL, due also to the three main bearing engine. I don't agree; I think the three models are close enough that superior engine and suspension tuning will determine the victor of any contest between them. Personally, I think all three models as sold to the public had atrociously mushy rides. Sport springs and a 50% stiffer compensating spring are listed in the W113 Workshop Manual and Technical Data books as options, but Americans never seemed to discover them. I guess too many W113s were gifts to wives and Stuttgart catered to it, at least in the USA. We know an increasing number were delivered with automatic transmissions and A/C every year. Now we come along and expect a little more of the car's "sportive" potential.
5) Longtooth's description of a car's lift during cornering is a risk for all automobiles however the 300SL Roadster and subsequent W113 SLs do reduce the phenomenon rather well by their low, single pivot differential. The very low pivot point successfully keeps the angle of the outside wheel (on a corner) negative (tipped in at the top) -- the most desirable angle due to tire roll. Separate parts between the body and suspension address lateral spring motion. The wide track is also helping. In 1987 I used a G-Force meter for tests on my 280SL and one of Carol Shelby's famous 289 Cobras over the same four mile loop of country roads. The 280SL recorded higher G-forces (just over 1 G) on all the sharper corners and nearly matched the Cobra's elapsed times despite 100 less horsepower. Both cars accepted controlled-drifts at will with negligible body lean, and the 280SL never rose on it's pivot axle. An open secret here (that all Mercedes owners should know) is never lifting the accelerator once it is applied in a corner. Lifting gives up the benefit of low pivot and negative angle of the rear wheels. With steady to increasing power, cornering is conspicuously superior to the fixed-axle Ferrari or Cobra. I'm sure all of this can be reduced to a mathematical model. M-B engineers undoubtedly did concoct the concept on paper first since they had to justify building a prototype low-swinging rear end before they could verify if it worked. When they got all done they (or the marketing whizkids) realized their typical clientele was more interested in a soft ride. ;-(
6) At the front wheels, suspension components intentionally tip the top of wheels inward of a curve as the wheels turn (more pronounced in the 1970s and till 1986), in anticipation of tire roll. Mercedes-Benz pooled their design with tire technology of the time which favored sidewalls strong enough to handle roll and tread going up the edge of each tire. Even with soft springs the W113 SL does what it is supposed to do ... deliver negative camber on the outside of corners. It's just that the "busy-ness" of the soft ride distract the driver from believing it!
[SIDE BAR: #6 is why flatter-bottomed tires with more abrupt edges, available since the early 1980s, are not well-suited to pre-1986s Mercedes-Benz. Flat bottom tires resist the roll a W113 is designed to "expect," and the flat bottoms very easily cause unwanted tracking diversions on crowned rural roads. The S-Class and SL Class did not fully adopt to the newest tires until 1986.]
7) When I read Jeff's "phase one installation report" on Sunday, trying out his new rear side springs at highway speed, I thought of a chart that I printed in my book and again in my SL Market Letter last month:
......................INCREASES......INCREASES
ADJUSTMENTS....OVERSTEER......UNDERSTEER
Ft. Air Pressure.....Higher..........Lower
Rr. Air Pressure.....Lower..........Higher
Front Camber.........More -.........More +
Rear Camber..........More +.........More -
Front Springs........Softer..........Firmer
Rear Springs.........Firmer..........Softer
Ft. Swaybar.........Thinner........Thicker
Rear Swaybar........Thicker........Thinner
Weight...............Rearward.......Forward
Front Tire Width.....Larger........Smaller
Rear Tire Width.....Smaller.........Larger
On any vehicle when stiffer springs are added to the rear only, it increasing potential for oversteer, all else being equal. This is why I always recommend changing all for corner springs. Introducing new sport or progressive rate springs to both ends at the same time avoids second guessing M-B's original front to back balance intentions. I'm not opposed to changing this relationship with thought but that is a separate decision unrelated to the present mission of less nose dive in braking and less body lean in corners, without a harsh boulevard ride. So Jeff and others, beware of more oversteer than you had before, until all springs are changed.
8) For Longtooth's question about how a non-tapered bar (coiled or otherwise) could still be "progressive" we may have to look to a "real" engineer for that answer, however I can tell you that my "progressive" springs are custom pitched to new angles at several intervals along the coil before the hardening process so the active coils differ in their angle to the descending weight where the loops are furthest apart. When placed in a spring tester the weight needed to squeeze the spring (deflection rate) increases progressively with every inch it is squeezed. Actually it becomes more complicated than that as the intended installed height has to be factored in first to deliver a prescribed curb height. Only after that is achieved can the desired beginning to ending deflection rates be programed (15 different calculations are involved for each custom order).
I hope this long winded dissertation is of some help. Please forgive any stupid typos they seem to be my foré and it's after midnight here!
Mit Vollgas (pedal to the metal)!
.....John
John R. Olson, Editor - SL MARKET LETTER
Snail Mail: 2020 Girard Av. So. Mpls, MN 55405
Phone: (612)-377-0155 - FAX (612)-377-0157
Website: slmarket.com - office@slmarket.com
1959 300SL Ro - 1977 450SEL 6.9 Wagon
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quote:
Originally posted by Longtooth
... You may note by reading the old automagazines when the 250SL came out vs the prior 230SL, one of the most dramatic and expected changes was to the suspension system... precisely because the 230SL had a high occurrance of suddenly losing the back-end unexpectedly (no warning by feel) on high speed cornering...
Longtooth
67 250SL US #113-043-10-002163
95 SL500
Thanks for the 230 SL defense, John!
I also was surprised with this Longtooth comment, because all the sources I have -in any case- say that 230 SL was the Pagoda with more sporty feeling and handling (less weight (1295 kg) than 250 and 280 (1360 kg), firmer front anti-roll bar, firmer (although with grease fittings) suspension parts instead of rubber...). And the Pagoda was always considered one of the cars with best road holding of its age.
I had the opportunity to test the handling of my 230 SL on a sport-driving-school track, and I found it very progressive. It was necessary to provoke the oversteering, and when it came, it was very easy and quick to control (with power steering):
(http://www.sl113.org/forums/uploaded/Albert-230SL/20038195340_Pago_sideways_L.jpg)
The only major change I have found in the W113 basic suspension components is: The front anti-roll bar diameter decreased from 22 to 20 mm in 250 SL from VIN 005164 (and for all 280 SL). According to John Olson's chart in previous message, a "Thinner front anti-roll bar increases oversteer", so is it the solution to the supposed "suddenly losing the back-end" problems :?: :?: :?: .
Maybe the softer bar was introduced in order to decrease the limit of the rear axle road holding, making the car even more progressive (= more warnings), comfortable, and easy to drive in the limit (they went from AMG to Elegance :) )? Anyway, it also decreased efficacy. I'm sure MB did this change against the taste of Rudolf Uhlenhaut, the original engineer of the Pagoda chassis and the racing "Silver Arrows" Mercedes. He loved the sporty handling and feeling of the cars!
According to the MB spare parts list, Longtooth's 250 SL (VIN 002163) should have the thicker 230 SL bar, so it has all the same 230 SL suspension system, and he seems happy with its handling! ;)
Regards,
Albert de la Torre Chavalera
Barcelona (Catalunya/Spain)
Feb.'64 230 SL Euro 113042-10-002432
Download Attachment: (http://images/icon_paperclip.gif) Pago_sideways_L.jpg (http://www.sl113.org/forums/uploaded/Albert-230SL/20038195340_Pago_sideways_L.jpg)
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Status Report-Progressive Spring Installation
Today I completed the installation of the compensating spring. I told someone else that I handled the compressed spring like it was a bomb. I had the put it under a lot of tension to make it fit. This project was made more difficult by the design of the progressive spring. It is more tightly wound at one end which made my compresser tool unable to fit near that end of the spring. I ended up tapping a piece of tapered wood into that end of the spring to separate the spring layers. With this accomplished I was able to fit the claw end and the compresser was able to do its job. You need to compress a 12 3/4 inch spring down to 10 1/4 inches to fit it in place. Had to take the tool apart and pry the claw ends out of the springs afer installation. In some ways the project was made easier because the new spring is 1 inch shorter than the old spring. The new spring and pads made a 1/8th inch change (lower) in wheel well height on both sides.
In addition to the above, I have changed all trailing arm bushings, front and rear, and installed progressive rear springs with new pads on both sides. Used the medium sized top pad for the rear springs. I placed the order in advance of taking it apart so I guessed at the pad size. It turns out the original pads were the smaller size.
I have a question for the group concerning shocks. In order to change the compensating spring you need to diconnect the top of the rear shocks. The shocks are gas filled so they remained in the extended position. I was able to reach up and grab the top of the shock and with one hand and some effort bring the piston down. Upon release the piston extended fully in about a second or two. The shocks seem sound otherwise, no leaking that I can see.
How do you know when it is time to change shocks? Do they degrade and then fail? or just simply fail? If I go by the Haynes manual my shocks are ok. What do you think?
Thanks,
Jeff
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I am really sorry to butt in here, but I feel I need to make an observation, and express my appreciation of being able to "lurk" or learn from this discussion.
I have attendend many Internet groups and forums before, often very technical (albeit on computing subjects).
I am very impressed by:- the level of technical knowledge in this forum
- the quality of writing in this forum (Longtooth, I think I have an inkling why you call yourself that but I do enjoy the quality and detail of your posts)
- and the cooperative atmosphere, without animosity, in this forum (John Olson, your reply was to the point, factual and untainted by emotion)
I have to say, this is extremely rare, on the Internet, in forums, newsgroups and other communities, and we all have to count ourselves lucky with contributing members like these.
Hats off to you all!
Peter
Check out http://bali.esweb.nl for photographs of classic car events and my 1970 280 SL
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This question is mostly for Longtooth.
If you were going to try to make a set of progressive springs with rubber blocks where would you place the blocks and how many should I use.
The reason I'm asking this is because I hope to be rebuilding my suspension soon and I thought I might tweak around with my old springs before buying new ones.
I know you would be just be estimating where the blocks would go but it would give me a place to start.
Bill Rader
'68 250SL
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Finished the installation of all five progressive springs this morning. Just got back from a test drive over a 20 mile course I often drive. I've got to tell you the springs were amazing. The suspension feels super solid. Body roll and braking nose dive have been greatly diminished. My 1970 280SL is very different driving car. I'd like to run a slolum course for time against someone with 33 year old springs. The rear end seems glued to the road. Any way I could go on and on about the springs.
I'd like to put out some comments for those who are going to do the installation themselves. Think safety, safety and more safety. Use a jack and jack stands that you can bet your life on. The job would be a lot easier and safer the second time around. I suppose that's always true. Study the Haynes manual and Mercedes CD instructions. They don't say everything but there pretty good. For those of you that have the Mercedes CD section 32-5, figure 32-5/6 shows a special adapter 111 589 00 63 00. This tool is very important when reinstalling the lower control arm. The bearing bolt has a tendancy, when lifting or lowering the lower control arm, to flip over. With the special adapter you can control this action and help align the bearing bolt with the front axle carrier. I made a tool for this by
taperring the end of a long 7/16 inch carrage bolt with a bench grinder. Aligning these bolts is dangerous and impossible without some sort of tool. Also you need a shallow 19 mm swivel socket to remove and reinstall the outer bearing bolt bolts. The bolts heads are partially covered by the control arm and difficult if not impossible to get off without it. Your going to need a extension for your ratchet as these bolts are on tight, as well the should be. This is the first time that I have ever seen lock washers completly flattened. Plan on replacing both sides for a total of 8 lock washers. The new front spring is 2 inches shorter than the old so it's easy to move into position.
I suggest you think long and hard about doing the compensating spring job yourself. Couple of things. The spring is under a lot of tension. Makes working around it kind of scary. Cheap Chinese spring compressor didn't help with the scary part.
This must be done after the trailing arms are reinstalled.
Take the top shock nuts off so you can so you can lower the axle halves as far as possible to relieve tension on the spring. Be very careful with tension on your brake lines. I used two additional jacks under the axle halves too make sure these lines were not stressed. My compressor had a very simple attachment which I used to keep the spring from bowing too much and flying off into who knows where. When reinstalling let the spring bow some when compressing the spring. When it is finally in place it is bowed some so this is not a concern. It also makes the compression a little easier. The new spring was 12 3/4 inches or an inch shorter than the old spring. You need to compress it to 10 1/4 inches to get it in place. I handled the compressed spring like it was a bomb. If I dropped it I was sure the Chinese tool would crack and the spring would end up in my ear. The tool worked ok when getting the old spring out. Difficulty arises when trying to use the tool on the new spring. The tool was designed in such a way that the claws that hold the spring were too large, especially for the tightly wound end of the spring. I used a tapered piece of wood to pry open the spring so that I could get the claw end in place. Sounds weird, but you will understand when you see the pieces you have to work with. I had to put a lot of pressure on this tool to compress the spring. Anyway I'm glad its done.
Spring pads:
I ordered spring pads prior to removing the old springs. I ordered the mid size rear pad and the only front pad listed on K&K's website. The old pad, which you may consider reusing, on the rear was
the thinnest version and the front pad was thicker than the only one listed by K&K. Right now the car sits up a little in the rear. Drivers side rear wheel well is 26 inches and the front 24 1/2 inches. I may leave it alone or change the rear back to the thinnest size pad. Don't know what more I can tell you about ordering pads.
For the rear end plan on replacing the rubber mount in the frame side of the trailing arm. It's a no brainer. I replaced the traing arm to axle bushings. One side was ok the other had some metal to metal chafing that I could not see because it was on top of the arm. So I'm glad I replaced them. It's a little tricky to reinstall the locking clip without the Mercedes fixture and an arbor press. I used a bench vise and a little block of wood. By the way, the nylon washers, axle and trailing arm surfaces were very rusty and corroded. This made them very stiff. Pland on using a wire wheel to clean this area.
That's all for now. If you have any questions let me know and I'll try to help out.
Jeff
1970 280SL 4 speed with new springs
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Jeff, In my opinion, that is one of thebest most lucid reports I have read on these forums. Thanks.
Rudy
Los Angeles
1971 280 SL
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Rudy,
Thank you for your comments. My earlier post was a bunch of random thoughts I wanted to put down somewhere in writing before I forgot the details. I hope they are usefull to those of you who are going to under take the job.
Changed the driver side rear spring pad from a 24mm to 18mm thickness. It made no change in wheel well height on the car. This spring and pad setup is a challenging one as described by John Olson. FYI, not including setup and clean up, it took me about an hour, wheels up to wheels down, to remove the rear coil spring and replace the top spring pad. Remember this was the second time for me so it went a "little" smoother.
Jeff
1970 280SL 4 speed
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For those of us that have ordered progressive springs I have located some information on the Mercedes CD having to do with Adjustments of Springs. The front and compensating springs ordered from John Olson are shorter than the stock springs. The progressive rear spring is the same height as the old one but I don't know what impact that may have on spring pads as per the CD. For this reason I don't know how applicable the CD will be in our situation. I offer the information for your consideration anyway.
The front and rear springs are color coded. You may have to clean the lower part of your spring but you sbould be able to find it. It is not on the bottom layer of the spring. In my case my front spring was marked with blue paint. According to the adjustment tables on the CD my car with two special equipments (power steering and A/C) should have pad # 111 322 05 85 and it does. This pad is 25mm in tall when measured 90 degrees counter clockwise from the molded spring end of the pad.
For the normal rear springs setup the CD describes red and blue colored springs. Red refers you to #108 325 01 85. This pad is 20mm when measured 90 degrees clockwise from the molded spring end of the pad. Mine happened to be colored blue which refers to # 108 325 01 85 pad. This pad is 14mm when measured the same way as the red version.
Conclusion:
The documentation on the CD agrees with the spring pad setup on my car. With the color code from your spring and the number of special equipment the documentation will tell you the part numbers for the spring pads on your car as it left the factory. This information would be uiseful if you wanted to order new pads prior to taking the car apart.
Conclusion 2
The progressive springs don't appear the agree with the factory tables for spring pads.
I learned a lot from the Haynes Manual and Mercedes CD. I'm going to take some measurements on my car tomorrow to see if I can determine what pads I need. Taking the car apart and trying new pads to improve the levelness of the car is a real pain. I hate trial and error. This may be how we will need to proceed in the end given the cars are different yet the same.
I'll let you all know what I find out.
Jeff
1970 280Sl 4 speed
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The "progressive" spring enthusiasts should enjoy their firmer springs and tighter ride.... as most if not all sports driving enthusiasts do, among which I include myself.
I've not visited this forum in quite some time so I was pleased to see John Olsen's response tonight (last nite... now this morning) and read it with interest.
1st, let me apologize to those with the 230SL model... my statement that the 230SL was more prone to loose it in hard cornering is based on articles I read many years ago (30?) from publications my father had collected beginning in '64, '65 thru the 280SL introduction in '68. I left Germany in '64 to return for University, and my father sent these articles to me in correspondance. ... most were German auto publications as I recall... some may have been from US publications later. I unfortunately cannot cite the precise dates, publications, or authors... the sources were German Automotive magazine articles on the order of Car & Driver. I can say that an MB engineer at the time would not have been inclined to agree with the articles, so it shouldn't surprise John Olson that his MB engineer source would tell him there was no truth to them even if there were. There's also the possibility that the genisis of these articles were propaganda to discredit MB by their competitors for which (at the time) one could cite English and Italien mfg'ers.... and the arch enemy in Germany... BMW.... to a much lesser degree at that time were the Porsche's competing with MB. I doubt the latter possibility was the only genesis however, as the propoganda campaign would have not endured without being debunked by other publications... and as we all know, MB in Germany has a strong and loyal market... both politically and economically, so it would be very surprising that a mis-information campaign by competitors could run without an equally large and more effective campaign financed by MB to dis- the mis-information.
Also, as Alfred correctly noted my mid year '67 250SL was mfg'ed with the 230SL suspension system.... while my father's '67 was mfg'ed near the end of the 250SL series. I've driven both cars.... as has my younger brother (who drove my father's 250SL extensively and to the extreme during the course of his mid-late teens while in Italy... where my family lived for 15 years). My brother, my father, and I have clearly and unequivacably notice that my 250SL leaves little margin for avoiding the rear end spinning out compared to my father's 250SL (this comparison was done in the period before my car was semi-permenantl garaged before restoring to it's now condition) . My brother-in-law (an avid BMW 6 series owner) also noted that my 250SL is less forgiving on extreme cornering than my father's (my brother-in-law purchased my father's 250SL from and owned it for 5 years). I have no doubt that the articles published about the 230SL being notoriously prone to spin-out without warning on hard cornering are true. When you push each to the edge, the earlier model will begin to spin out and with increasing moment (faster) with less time/ability to correct.
Albert also cited the thinner front torsion bar as the single major published difference in the 230SL & the later series W113's suspension system. He also notes correctly that the thinner torsion bar is less stiff (the one on the later 250's and subsequent versions) ... but it's not just a little less stiff... it's a lot less stiff. 22mm diam vs 20 mm diam appears to the non-professional to be only a 10% reduction in 'stiffness'... but in fact the stiffness is a function of the cube of the thickness... or in the case of a cylindrical object, the 4th power of the radius. So the 10% reduction in the torsion bar's radius means it was much less stiff --- in the range of 70% as stiff as the larger diameter one. This means that the front end is allowed to tilt more with the thinner torsion bar on cornering (front end can tilt more than back-end.... i.e. the frame's torsional resistance)... which gives the driver a greater degree of 'feel' as the car progressively reaches it's limits.... i.e. greater warning before the back-end breaks loose.
By it's very nature, the stiffer the car's suspension system the closer the car can get to it's limits of control (i.e. as in spin-out limit) with very little other indication that this limit is being approached.... even if it's limit is increased over that of the less stiff suspension system.
Of course this is an advantage in racing and competitive applications, but it none-the-less makes the car's handling ability more risky for drivers without racing or extreme driving experience. This was and is of major concern to auto manufactures.... since their sales of these types of cars are dominantly to wanna-be's and/or the wives of wanna-be's that can afford them.... and they can ill afford to get a reputation for 'bad' handling among their dominant market. With the exception of the 300SL MB has almost invariably and purposefully catered to the luxury market in post war production .... softer, spongier rides. I agree whole-heartedly with John's opinion that "all three models as sold to the public had atrociously mushy rides."
It was not, nor is it my intent to detract from the 230SL in favor of later versions. Enthusiasts of the W113 will note that the original 230SL styling and driving capabilities were not enthusiastically endorsed at the time.... softening the ride, giving it more horse-power, were marketing methods to give it wider market appeal in Germany and in the US market.... a 'grand touring' sports car was a marked brake from the 300SL (a real sports car with limited sales) and a major improvement over the mass appeal of the 190SL. To this day MB doesn't market a 'sports' car in the regime of the latest round --- M3 (now M4's), S2000's, Porsches, etc.... The closest they come, and it's a far cry, is the SL55's now.... not marketed to the same market segment as the other 2 seater sports cars.
A few more comments regards some of John's statements.
1) "An open secret here (that all Mercedes owners should know) is never lifting the accelerator once it is applied in a corner. Lifting gives up the benefit of low pivot and negative angle of the rear wheels."
This is true of all rear-wheel drive / front engine cars in general, not just MB.... some more than others, depending on weight distributions. The driving forces during cornering are from the rear wheels 'pushing' the car thru the turn. When the accelerator is lifted in the turn the engine speed reduction puts a brake on the rear driving wheels... i.e. deceleration. This action is tantamont to applying the brakes to the rear wheels without braking on the front wheels... though the braking action by deceleration is less than actually braking. While in the turn the front wheels are trying to turn the car (from an engineering view... the turned front wheels are pushing the front of the car side-ways in varying degrees depending on how far the front wheels are turned... while the rear wheels are trying to push it straight ahead. A body in motion tends to stay in motion in the diretion of it's motion. When you brake the rear while pushing the front to the side, the car (body) has more than just a little tendancy to spin out ... i.e. the rear tends to keep going in the direction the wheels are turning while the front is being pushed side-ways (relative to the rear).... that's a spin-out when the rear looses grip. The more you decelerate in the turn the closer the body gets to it's traction limits with the road. Keeping the rear and/or front wheels from rolling over is an effort to minimize the effect.... hence the desire for minimizing wheel tilt (axle tilt).... wider wheel-base, stiffer suspensions... which also bring the car closer to the edge without giving warning signs.
There's no doubt that a W113 can take higher G's without spinning out than a Cobra.... but this is dominantly due to the W113's wider wheel base... and probably if the facts were known, also to it's more centered weight distribution. I don't have fact sheets on the Cobra but 2 weeks ago I had the opportunity to be up-close and personal with 2 of them (being used in to take pictures for a future promotional marketing campaign at the co. I work for)... both used in current racing among the Cobra enthusiast crowd. From observation only.... and there's not too much that's not fully visible on a Cobra... I'd guess that the weight distribution is closer to 60/40 --- front / rear.... and the wheel base is much, much narrower than the W113's. The degree to which the swing axle suspension on the W113 plays in ability to achieve higher cornering G's than the Cobra may in fact be an artifact of the other conditions in setting up the cars than the swing-axle to which John appears to give the lions share of the credit if not all the credit.
As to the 'progressive' description of the springs John sells...which was the topic of my original interest in this thread... I believe John cites the nature of all springs, coil or otherwise, when he states once again (as is similarly expressed on his web-site):
"When placed in a spring tester the weight needed to squeeze the spring (deflection rate) increases progressively with every inch it is squeezed."
I have previously cited the engineering principles of steels and any other material in any form related to their deflection under force... and the equations governing these relationships and unless or until the material reaches it's in-elastic limits (at which point it begins to permanently deform and won't recover to it's orginal dimensions), or begins to bottom out on itself (i.e. one coil bottoming on another...metal-metal contact), the spring behaves as all springs... regardless of changes in winding pitch between the end points, or diameters, or "custom pitched to new angles".... These variables only change the stiffness ... they don't give it a progressively increasing spring rate.
Should John once again puruse this forum and topic, I repeat my original request to simply provide the force vs displacment curves he cites as being measured by the spring mfg'er in spring tester.... more usually referred to in the engineering community as a 'tensile testing' machine.... which can either push on or pull on the object being measured (i.e. applying compressive or tensile forces on the object). Such tests have to be repeated in 2 successive tests to show that the object has not gone beyond it's elastic limits such that the at rest dimension after the 2nd application of forces is identical to the dimension at the start of the 1st test sequence.
I believe it's more probable that John's application and use of the word 'progressive' is not being applied to mean an increasing spring rate as function of force applied...rather it's being used to mean that the displacement is progressivly greater as the force is progressively greater.
By the way... what is the spring rate of these 'progressive' springs John sells? The spring rate isn't shown on the Web-site nor has it been cited in comparison to standard springs or the off-the-shelf higher stiffness springs optionally sold by MB as "Special Versions: 1) Harder Springs for Bad Road Conditions, PN 113 324 02 04", compared to Standard Springs PN 113 324 04 04.
MB sold several optional springs for front and rear.... for SLs various combinations of extra's... from none to 2 optional extra's.... auto trans, power steering Air conditioning, etc. I surmise these were springs to compensate for added weight of these extra's.
Longtooth
67 250SL US #113-043-10-002163
95 SL500
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I can't believe I'm getting drawn into the technical side of this but...
Longtooth - it seems your analysis is based on a deflected beam. A coil spring is effectively a torsional bar. Perhaps your equations would work out differently in this case.
PaulS
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Am I the last to install these springs? Have been following the thread in anticipation of my installation next summer. Surely there are others with worthwhile installation experiences to add (as opposed to spring theoretical issues). -JP-
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My experience with the springs is documented in this thread. If I can answer any questions you have please let me know. Good Luck!
Jeff
Jeff Clute
1970 280SL 4-speed
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Jeff,
I am pleased to read your response regarding the springs. I put these springs on about 18 months ago and was just amazed with the difference. I have said this before and can say it again-the progressive rate springs are the single best enhancement I have made to this car (and I have done a lot!). Glad to see that others share my enthusiasm for this enhancement.
Best,
Tom
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My new Olson springs were installed November 13-14 at H&M Autohaus, where handling the compensating spring, establishing the proper ride height, and determining the right spring pads is old hat. So I don't have any installation stories to tell, but I am happy to share my initial reaction to these new springs:
1. Visually, the springs re-established the original, more aggressive stance that, in my car at least, had fallen victim over the years to the front end creeping up and consequently making the rear end look too squat. Between John Olson's springs and H&M's installation, I think the car looks just about perfectly balanced again.
2. In city driving, I've felt a slightly firmer, more mated-to-the-road ride which to me is much closer to the original feel of the 230SL. I was never one to call the 280SL's ride mushy, but I can't imagine anyone calling this car soft-riding now.
3. Under hard braking, the notorious front-end dive is about 40% gone. Over the years I'd grown to feather my braking to mask or minimize the effect of the dive, but now it's less of an art and more of a technique. I suspect the drivers around me are less likely to conclude that every time I brake it's an act of panic.
4. As to cornering and handling, here's a simple-minded observation: since the car was new, I've always been able to take curves and exit ramps at a little less than 50% above the posted speed recommendation (i.e., if it's a 45 mph ramp, I've not been afraid of 60 mph). But now my confidence level, on the same curves I've negotiated before, is almost exactly at 50%. That's a huge, huge improvement to me.
I don't know about deflection rates and such, and I can't claim that my old springs were fatigued, but this feels much more like the car I bought in 1971 than it ever has. So far I don't detect a tendency to oversteer or understeer that wasn't there before -- but I do detect a more nimble and willing car overall.
Bill Greffin
Chicago
#22375